Mirrors and reflection of light — GCSE Physics practice questions

Question 1

A dancer practises in front of a large flat mirror on the wall of a studio.

Which row describes the image of the dancer formed by the mirror?

Accepted Answer

C: virtual · same size. A plane mirror forms a virtual image: the reflected rays only appear to come from a point behind the mirror, so the image cannot be formed on a screen. The image is exactly the same size as the dancer, upright and laterally inverted.

Question 2

In a hair salon, a customer sits 1.4 m in front of a large flat wall mirror.
The hairdresser stands directly behind the customer, 0.50 m further from the mirror than the customer.

How far is the hairdresser from the image of the customer?

Accepted Answer

D: 3.3 m. The image of the customer is 1.4 m behind the mirror. The hairdresser is 1.4 + 0.50 = 1.9 m in front of the mirror. The distance from the hairdresser to the image is therefore 1.4 + 1.9 = 3.3 m.

Question 3

A laser-cut acrylic sign is tested with a ray of light. The diagram shows the ray passing from air into the acrylic.
The angles marked are measured from the surface of the acrylic.

What is the refractive index of the acrylic?

Accepted Answer

C: 1.49. The angles of incidence and refraction are measured from the normal: i = 90° − 40° = 50° and r = 90° − 59° = 31°. Then n = sin 50° / sin 31° = 0.766 / 0.515 = 1.49.

	type of image	size compared with the dancer
A	real	same size
B	real	smaller
C	virtual	same size
D	virtual	smaller